Strange TWChoose.ar behavior

Questions
1

Hi all, I’m getting some odd behavior with TWChoose. The weights array is [0,1], so I think I should hear only noise. But, I’m hearing occasional fragments of a sine tone. Oddly, if I swap Dust for Impulse, it seems to work as expected. I’m on SC 3.11.0, macOS 10.14.6. Is this a bug, or am I doing something wrong?

Eli

(
{
	TWChoose.ar(
		Dust.ar(20),
		[
			SinOsc.ar(200),
			PinkNoise.ar(1)
		],
		[0,1]
) * 0.1!2;
}.play
)
1 Like
2

There is a bug in TWIndex (which is used in TWChoose), which I only just noticed: a variable sum should be initialized to 0 once per trigger, but it’s initialized only once per control block. If there happens to be more than one trigger in a control block, the 2nd, 3rd etc triggers will go to index 0.

I think I can put in a fix later today.

The other potential issue is: if the random number generator produces exactly 0, then it would also go to the first index. But that should be exceedingly rare and almost unreproducible.

hjh

3

BTW this reproduces the bug:

a = {
	var trig = Impulse.ar(ControlRate.ir * 4),
	index = TWindex.ar(trig, [0, 1]);
	Poll.ar(trig * (index <= 0), index, "failed");
	Line.ar(0, 1, ControlDur.ir, doneAction: 2);
	Silent.ar(1)
}.play;

failed: 0
failed: 0
failed: 0

4 triggers should be generated. The second, third and fourth in the kr block calculate incorrectly.

hjh

4

Unfortunately, build requirements have become more complex lately, so it will take me some time to update my environment. So it’s definitely not going to happen today.

hjh